Tube lift mechanism



Oct. 3, 1967 R. w. SHAWFRANK TUBE LIFT MECHANISM 2 Sheets-Sheet 1 FiledOct. 22, 1965 Inventor- Robert W.5hawrc\nk .fi'll'or'ne ls Oct. 3, 1967R. w. SHAWFRANK TUBE LIFT MECHANISM 2 SheetsSheet 2 Filed Oct. 22, 1965Inv encor- Robert W. Shawfrank.

' fitter-megs United States Patent 3,345,025 TUBE LIFT MECHANISM RobertW. Shawfrank, Des Plaines, Ill., assignor to The Shawfrank EngineeringCorporation, Des Plaines, Ill., a corporation of Illinois Filed Oct. 22,1965, Ser. No. 501,938 5 Claims. (Cl. 248123) ABSTRACT OF THE DISCLOSUREA tube lift mechanism for supporting and vertically locating a cathoderay tube or similar article on a portable exhaust cart duringfabrication of such article. The lift mechanism is effectivelycounterbalanced at all set positions to provide smoothness of operationand accuracy of positioning and incorporates a pair of vertical supportcolumns telescopically received Within associated sleeve guides which,because of the interfit therebetween, permits the accommodation ofcathode ray tubes or other objects of differing weights with apredetermined weight range without adjustment.

This invention relates in general to portable exhaust carts of the typesuitable for use in the fabrication of cathode ray tubes and moreparticularly to an improved tube lift mechanism for such exhaust cartsfor vertically locating cathode ray tubes of varying size and weightsthereon with smoothness and accuracy prior to drawing a vacuum andsealing ofl? the tubular portion of the tube.

In the manufacture of cathode ray tubes, either monochrome or color, thetube envelope is usually fabricated first and the gun structure issubsequently joined to the envelope. The tube is then exhausted and thetubulature sealed off at the neck portion to provide an evacuated andoperational tube. The usual practice is to provide a hollow glass pipeextension, commonly referred to as the exhaust tubulature, at the baseof the neck, thru which the tube envelope may be conveniently evacuated.Upon reaching the proper degree of evacuation, the tubulature is heatedin a sealing area and collapses inwardly in that area to seal off thetube.

Prior to sealing, the cathode ray tube must be baked in an oven chamberto drive out gases from the aquadag coating, the gun assemblies, andother internal parts. A separate heating device, commonly referred to asa tipotf oven, is employed to apply the required heat locally to theexhaust tubulature to effect sealing of the same at the proper time.During the fabrication operation, the baking operation, and particularlyduring the time the exhaust tubulature is being sealed off, the cathoderay tube must be carefully supported. In addition, the cathode ray tubemust be vertically located or positioned on the exhaust cart so that theexhaust tubulature engages and disengages the exhausting system andtip-off oven structure. This requires particularly delicate positioningbecause of the fragile nature of the exhaust tubulature (being formed ofrelatively thin-walled glass) and alignment requirements of the tubepins. The tube lift mechanism therefore must exhibit smoothness ofmovement as well as permit accurate control over very small incrementsof vertical movement for alignment purposes. In addition, it isdesirable that the lift mechanism :be capable of accommodating differenttypes of cathode ray tubes having differing weights, within apredetermined range, without requiring individual adjustments for eachweight.

Heretofore, the vertical positioning of the cathode ray tubes on suchexhaust carts has been commonly achieved by tube lifts with rack andpinion gear arrangements or negator springs coupled between the supportstructure for the tube and the cart frame. These prior arrangements,

3,345.25 Patented Oct. 3, 1967 however, have proved less thansatisfactory. This has been principally because of the inability ofthese devices to provide movements of sufiiciently small increments andsmoothness of movement for the cathode and to accommodate cathode raytubes without requiring individual adjustments.

In accordance with a preferred embodiment of the present invention, atube lift mechanism is provided for Ea portable exhaust cart wherein atube support frame or yoke seats on the bell portion of the cathode raytube and in turn is supported by a pair of vertical support columns.These columns are telescopically received within associated sleeveguides anchored to the cart frame. The columns themselves are supportedby a pair of lever members pivotally supported from the cart frame atapproximately their centers. Each lever includes a stop, such as acircular cam or roller, at one end to engage a face formed at the bottomof the vertical support column. A counter weight is positioned at theother ends of the lever member so as to be supported therebetween. Thecounterweight thus moving downwardly as the supported tube is movedupwardly, and vice versa. In one embodiment of the present invention,the counterweight is pendulously supported from a pivot point near oneend on each of the lever members and hangs vertically therefrom at allset positions of the lever members rather than rotating in unison withthem. In still another embodiment, the aforementioned counterweightstructure utilizes a cylindrical member with a hollow core into whichmay be inserted additional selected weights in the form of a solid rod.The inner insertable rod Weights rolling within the hollow outer weightunder the influence of gravity to again maintain the center of gravityof the counterweight structure in vertical alignment with the pivotpoint on the end of the levers. The sleeve guides are constructed tohave a friction-fit on the slidable vertical support columns and providesufficient frictional resistance to movement to hold the liftingmechanism unit in any one of the Various set positions. It has beenfound that this balancing action takes place even with substantialvariations in tube Weight. iIn addition, unusual smoothness of movementfor the ;lift mechanism as a whole is achieved,- permitting the operatorto impart very small increments of vertical movement of the cathode raytubes supported on the exhaust cart.

Accordingly, it is an object of the present invention to provide animproved cathode ray tube lifting mechanism for an exhaust cart which iscapable of small increments of vertical movement and characterized bysmoothness and accuracy of such movement.

Another object of the present invention is to provide an apparatus ofthe above type that accommodates cathode ray tubes of diifering weights.

A more particular object of the present invention is to provide anexhaust cart with an improved tube lift mechanism of the foregoing typewherein lever means, pivotably supported intermediate their respectiveends, pendulously support a counterweight at one end thereof and aslidable vertical support column at each of the other of the respectiveends between which a cathode ray tube or smilar article may be supportedand moved between predetermined limits of vertical travel.

Still another object of the present invention is to provide an improvedtube lift mechanism for an exhaust cart of the foregoing type whereinvertical columns supporting the cathode ray tube interfit withassociated sleeve guides in a manner effective to hold the tube orsimilar article within a given range of weights in any selected verticalposition.

Still another object of the present invention is to provide an exhaustcart for cathode ray tubes with an improved tube lift mechanism whereinthe counterweight 3 has a hollow core adapted to receive selectedweights therein so as to extend the range of the tube weights that canbe accommodated.

It is a further object of the present invention to provide an exhaustcart for cathode ray tubes with an improved tube lift mechanismutilizing features of construction, combination, and arrangement whereina simple, effective and readily manufactured structure is provided, tothe end that a product of maximum commercial usefulness is achieved.

The novel features which are believed to be characteristic of thepresent invention are set forth with particularity in the appendedclaims. The invention, itself, however, together with further objectsand advantages thereof, will best be understood by reference to thefollowing description taken in conjunction with the drawings, in which:

FIGURE 1 is a perspective view of an exhaust cart having a tube liftmechanism constructed in accordance with the present invention;

FIGURE 2 is an enlarged fragmentary view in crosssection showing theexhaust chuck and tip-off oven assemblies;

FIGURE 3 is an enlarged fragmentary view of the exhaust tubulature andneck portion of a cathode ray tube;

FIGURE 4 is a fragmentary elevation view from the side showing the tubelift mechanism in the fully lowered position;

FIGURE 5 is a fragmentary elevation view from the side showing the tubelift mechanism in the fully upraised position;

FIGURE 6 is an enlarged fragmentary view in crosssection of a sleeveguide and associated support column;

FIGURE 7 is a fragmentary view in perspective of a counterweight with ahollow core;

FIGURE 8 is a diagrammatic representation of a portion of the lever andcounterweight in different set positions; and

FIGURE 9 is a view from the side in partial cross section showing thehollow core counterweight and additional weight inserted therein.

Referring now to the drawings, an exhaust cart 10 is shown in FIGURE 1constructed in accordance with a preferred embodiment of the presentinvention. The cart 10 includes a four-legged frame 11 having a bottomtray 12 and a top or table 13 and a caster 14 under each of the legs.The underside of the cart table 13 provides a convenient space toaccommodate the necessary electrical control equipment such as fuses,terminal boards, relays and the like, such associated equipment notbeing shown in detail as it forms no part of the present invention. Avacuum pump 15 may be mounted in the bottom of the tray 12 andcontrolled by any suitable means, such as an electric motor 16 which maybe mounted adjacent thereto in the manner shown.

The cart 10 further includes a pair of inverted T-shaped sleeve guides20 (FIGURES 4, 5 and 6), which guides include a flange portion 20a and atubular portion 20b extending perpendicularly therefrom. The top orforward end of the tubular portion 20b includes a shoulder 20s followedby a threaded section 2th (best shown in FIG- URE 6). The flange portion20a is adapted to be atfixed to the cart, such as to the underside ofthe table 13. The flange portion 20a is secured thereby by mountingbolts 21 with the tubular portion 20b of the respective guides 20extending upwardly thru clearance holes in the table 13. Each of thesleeve guides 20 is adapted to slidably receive an associated supportcolumn 21 therein and maintain the same in vertical alignment. Each ofthe columns 21 includes a U-shaped flange or support yoke 23 (FIG-URE 1) at the top end with the arms facing inwardly in the manner shown.The support yokes 23 are adapted to support a cathode ray tube 24therebetween with tips or arms of the yokes bearing against the bellportion of the tube 24.

The cart 10 further includes an exhaust chuck assembly 4 (best seen inFIGURE 2), a tip-off oven assembly 32 and an R-F coil assembly 34, thefunction of which will be sub equently explained. The R-F coil assembly34 consists of a rectangular base plate 34a of a length to overlay thetops of the sleeve guides 20 (FIGURE 1). Suitable clearance holes may beprovided in the base plate 34a so as to receive the forward threadedportion 20t of the sleeve guides 20 therethrough and rest on theshoulder portion 20s as shown in FIGURE 6. A mounting nut 35 is threadedon the sleeve 20 to hold the mounting plate 34a and in turn maintain theoven assembly 34 securely in the position as shown in FIGURE 1, the R-Fcoil assembly 34 includes a centrally located opening 340 through whichthe neck portion 2411 of the tube 24 may extend (FIGURES l and 2).

The tip-off oven assembly 32 includes a disc 32a constructed of asuitable thermal absorbant material, such as ceramic, which has aplurality of heater wires embedded therein (not shown). The heater wiresare supplied electrical power through the pair of supply terminals 32tlocated on the side of the disc 32a (FIGURE 2). The disc 32a furtherincludes a central opening 32b through which the tubulature 24! maypass. A plurality of pin receptacles ring the periphery of the discopening 32a for receiving the various tube pins of the cathode ray tube24. The pin receptacles enable the base of the tube 24 to be securelyheld in an immobilized position throughout the various steps andoperations performed on the tube 24 as described below.

The disc 32a is mounted on a horizontal support arm 32c and, in turn,the arm 320 is mounted on a vertical shaft 32s. The shaft 32a is hollowso as to permit electrical contors 32 w to pass therethrough and supplythe necessary electrical power to the disc 32a. The shaft 32s ismaintained in vertical alignment by a sleeve guide 36 affixed to theunderside of the table 13 as shown. A U-shaped support bracket 38,having one leg thereof affixed to the underside of the table 13,includes openings in the respective legs through which the shaft 32sextends. The limits of vertical travel for the shaft 32s, and in turnthe oven assembly 32, are determined by collar stops 38a aflixed aboutthe shaft 32s in the manner shown. A resilient helical spring 37 isinsertable over a bottom portion of the shaft 32s, bearing against thebottom leg of the bracket 38 and the top one of the collar stops 3801,thereby providing a bias for the oven assembly 32 in the upwarddirection. Thus, with this construction, the tipotf oven assembly 32 isseen to be rotatable about the shaft 32s for horizontal alignment andmovable in a vertical direction against the action of the spring 37between the limits as set by the respective collar stops 38a.

The exhaust chuck assembly 30 includes a cylindrical, hollow chamber30a, open at the top and externally threaded about the rim to receive anassociated cap or cover 40. A shoulder or flange 42 is selectivelypositioned internally of the chamber 30a, e.g., approximately a third ofthe distance down from the top. The flange 42 includes a central opening42a to permit the tubulature 24t to pass therethrough, as shown inFIGURE 2. The flange 42 serves to support a block of resilient material43, such as rubber, which is cylindrical in shape to fit snuggly in thechamber opening above the flange 42. The function of the rubber block 42is to serve as a seal when the tube 24 is being evacuated. The rubberseal 42 includes a central opening dimensioned to receive the tubulature24t therethrough with minimum clearance but without binding. The rubberseal 42 extends slightly above the top edge of the chamber 30a so thatwhen the cap 40 is screwed down tightly, the seal 42 is sphericallycompressed between the cap, flange and side walls. The result is that aneffective seal is provided along the length of the tubulature 24t incontact with the sides of the central opening in the seal 43.

The tube itself is evacuated by the vacuum pump 16 connected to thechamber 30a by the airline 44 composed of copper line or the like whichis coupled into the chamber 30a by an airtight connector assembly 45. Apetcock 46 may be provided at the bottom of the chamber 30a to drain offmoisture condension that may collect during the evacuation processes forthe cathode ray tubes. The chamber 30a is suitably affiixed to the tabletop 13, such as by angle brackets 47 or the like.

In the fully lowered position, in which position the cathode ray tube 24may be evacuated, the tubulature 242 extend-s through the centralopening of the rubber seal 43 into the lower compartment of the chamber39a. In this position, best seen in FIGURE 2, the pins of the tube 24are received in the associated pin receptacles of the tip-oven assembly32 and the R-F coil assembly 34 is positioned adjacent the gun assemblyof the tube 24. With the tube 24 in this position, the entire cart maybe passed through an oven chamber (not shown) wherein the gasses may bedriven from the various internal parts. In addition, the R-F coilassembly 34 may provide relatively intense heat locally about the gunassembly 24g. At an appropriate time, the tip-off oven assembly 32 isenergized so as to provide a relatively intense heat locally to aportion of the tubulature 24t, such as that indicated by the cross-hatcharea 24x in FIGURE 3, whereby the area collapses inwardly under actionof the vacuum and effectively seals off the tube when it is allowed tocool and solidify.

After the tip has been sealed, the tip-off oven 32 is depresseddownwardly and the sealed portion of the tubulator 241 is scratched witha file or the like and broken off. The sealed-off tubulator portion maybe left in the exhaust chuck assembly until the tubulator of a newcathode ray tube is to be inserted.

The improved tube lift mechanism constructed in accordance with thepresent invention is indicated generally at 50, best seen in FIGURES 4and 5. The lift 50 includes a pair of vertical members 52 suitableaffiXed to the underside of the table 13 and extending downwardly atopposing sides of the frame 11. A pivotable lever arm 54 is suspended onthe bottom end of each of the members 52. The arms 54 are attachedintermediate their ends by a pivot pin 55. The lever arms 54 and thevertical members 52 may be conveniently formed from conventional anglebracket stock or other materials may be used if desired.

Each of the lever arms 54 includes a roller 56 at the one end thereofadjacent to the bottom end of the vertical support columns 22. Amounting bolt or pin 56a secures the rollers 56 to the lever arms 54 andserve as axles therefor. The opposite ends of the lever arms areutilized to support a counter-weight 58 therefrom (FIGURES 1, 4 and 5).In this embodimengthe counterweight 58 includes a pair of flanges ortabs 58a extending upwardly at respective ends of the counterweight andsubstantially normal to the longitudinal axis thereof. Mounting bolts orpins 58b extend through suitable clearance holes provided in the arms 54and the tabs 58a whereby the counterweight 58 is pendulously supportedin the manner shown in FIGURES 1, 4 and 5. That is, the counterweight 58is thus allowed to swing about the pivot points formed by the pins 58bas the lever arms 54 are pivoted about the pivot pin 55. The result isthat the center of gravity of the counterweight 58 is maintained incontinuously vertical alignment with the pin 58b at all set positionsfor the tube lift mechanism 50.

At the other end of the lever arms 54, the vertical support columns 22include a flat base section 220 which has a horizontal dimensionsufficient to ensure that a portion thereof overlays the center of theroller 56 at any set position of the lever arms 54. The base 220 thuscontacts the roller 56 at a single point on the periphery thereof, apoint which is at all times in vertical alignment with the pivot pin 56aacting as the axle. The result is that the weight of the tube 24 and thevertical support columns 22 produce a force which is always actingdirectly on the pin 56a.

It will be appreciated that a moment of force is produced at therespective ends of the lever members 54 which act directly on the endpivot points as represented by the pivot pins 56a and 58b. The result isthat for a given counterweight 58 and cathode ray tube 24, a balance ismaintained for the tube lift mechanism 50 at all set positions becauseof the moments produced at pivot pins 56a and 58b being substantiallyequal.

This all-point balance would not occur, however, if the counterweight 58were not pendulously supported about the pivot pin 58b, but were rigidlyand non-rotatably suspended from the end of lever members 54. In thelatter condition, the center of gravity of the counterweight 58 wouldnot be maintained in direct vertical alignment wit-h pivot pin 58b butwould be progressively shifted therefrom to one side or the other as thetube lift mechanism 50 is moved from the completely horizontal position.This can be more readily appreciated by reference to FIGURE 8. As thelever member 54 is moved downwardly from the horizontal position H toone such as indicated as HV, it will be seen that the counterweight 58swings counterclockwise from a position perpendicular to lever member 54to one forming an obtuse angle thereto, thereby maintaining the centerof gravity of the counterweight 58 in direct vertical alignment with thepivot pin 58b. Should the counterweight 58 be nonrotably suspended fromthe lever member 54, and thus remain in a position perpendicular theretoas in the fully horizontal position H, the center of gravity forcounterweight 58 would be shifted, when viewing FIGURE 8, to a positionalong the dotted line X when moved to the position HV. This shifting ofthe center of gravity to the left would thus produce a moment of forcewhich would be less than that as produced by the vertical columnarsupports 20 and the cathode ray tube 24 acting on the came roller 56,and in turn, on the pivot pin 56a, thereby creating an imbalance in thesystem.

It is not, however, to be inferred from the foregoing that only cathoderay tubes of one specific and definite weights may be accommodated for agiven counterweight. 0n the contrary, one of the advantages of the tubelift mechanism constructed in accordance with the present invention isthat cathode ray tubes within a predetermined range of weights may bevertically positioned by the tube lift mechanism 50 with smoothness andaccuracy without further adjustments of any kind being necessary. Anydifference in weight between the counterweight 58 and a particularcathode ray tube 24 (within the aforesaid weight range) that may bepresent is effectively compensated for by frictional forces introducedinto the system, principally by the interaction of the sleeve guides 20with the vertical support columns 22. In the preferred form, the guides20 telescopically receive the columns 22 therein, respectively, and areconstructed so as to provide a friction interfit therebetween. Thisfriction interfit between guide 20 and vertical column 22 provides apredetermined resistance to movement which must be overcome in order toeffect any change of position for the lift mechanism 50 and is effectiveto maintain the mechanism 50 in its set position despite a difference inweight between counterweight 58 and a cathode ray tube 24 supported bycolumn elements 22. It is to be emphasized, however, that the value ordegree of clearance between the guides 20 and column elements 22 is notcritical and may be varied within limits without departing from the truescope of the present invention. Moreover, other frictional forces maylikewise be introduced into the system from other sources to supplementthat as provided by the guides 20 and column elements 22. For example,additional resistance to movement may be provided at the pivot points55, 56a and 58b if desired.

With a tube lift mechanism 50 thus described, cathode ray tubes ofdiffering weights may be effectively accommodated without additional orfurther adjustment being necessary. In practice, it has been found thatcathode ray tubes having a surprisingly large variation in their weightsmay be vertically located in any desired set position on the portableexhaust cart 10 with comparative smoothness and accuracy. A cathode raytube 24 with a higher weight will produce a sinusoidal momentcharacteristic which is shifted upwardly and a tube with less weightwill produce such a curve shifted downwardly. However, as long as thedifference between the moment characteristic of the tube 24 pluscolumnular elements 22 and the moment characteristic of thecounterweight 58 does not exceed the resistance to movement effected bythe friction interfit between guides 20 and columns 22, the mechanism 50will remain in that position when so set. No further adjustments of anykind are necessary to compensate for the differing weights of thecathode ray tubes within this predetermined range.

The support columns 22 are preferably constructed of a rust-resistantmaterial, such as stainless steel, or the like, while the sleeve guides20 may be formed from common cold rolled steel stock, since the innerbearing surface contacting the columns 22 are not exposed to the ambientatmosphere. Other materials may be used, of course, without departingfrom the true scope of the present invention.

It is also to be emphasized that the frictional interfit between theguides 20 and columns 22 additionally serves to provide the unusualsmoothness of vertical movement as well as the capability of effectingrelatively small increments of such movement which characterize the liftmechanism of the present invention. In order to change the position ofthe mechanism 50, a certain minimum force must be applied, that is, aforce which exceeds the resistance to movement caused by the friction,plus or minus the difference between the moments of force being producedat opposing ends of the lever members. This will be seen to effect moreuniform acceleration and de-acceleration for the lift mechanism as aunit and thereby minimize overshoot and the inherently jerky motionordinarily to be found in the more free-swinging systems. Thisminimizing of the overshoot is quite essential in the ability of theleft mechanism to effect small increments of vertical movement for thepositioning of the cathode ray tubes 24.

From a purely theoretical viewpoint, it cannot be said with absolutecertainty the precise factors giving rise to the unusual smoothness ofthe operation exhibited by the lift mechanism of the present inventionand the accuracy with which a cathode ray tube may be verticallypositioned upon the exhaust cart. An important contributing factor,however, must necessarily reside in the fact that the lift mechanism 50maintain a dynamic balance as well as a static balance. This dynamicbalancing effect arises from the fact that the counterweight 58, inbeing pendulously supported as previously described, always swingscounter to the arc of rotation imparted to the lever members 54. Thatis, as the lever members 54 are pushed downwardly (viewing FIGURE 8),thereby tending to impart a clockwise rotational are to counterweight58, the force of gravity operates to swing the counterweight 58 in acounterclockwise direction from its position perpendicular to levermember 54 when in the fully horizontal position to one which maintainsits center of gravity in vertical alignment with pivot pin 58b. Theresult is that the angular momentum that would otherwise be imparted tocounterweight 58 is thus compensated for or negated and overshoot of thelift mechanism 50 thereby effectively avoided or minimized. Thiscompensation characteristic becomes particularly advantageous forcounterweights of significant mass and weight and in instances when itis desired to move the lift mechanism 50 at a rapid rate from one setposition to another.

Cathode ray tubes of increasing weight ranges, as previously mentioned,may also be accommodated by the lift mechanism 50. That is, tubes havinga weight which produces a moment of force at one end of each of thelever members 54 which exceeds the moment of force produced by thecounterweight 58 at the opposing ends thereof by an amount greater thanthe resistance to movement presented by the frictional interfit betweenthe guides 20 and columns 22. To this end, the counterweight 58 may beconstructed so as to include a hollow core extending along a substantialpart of its longitudinal dimension and having an opening at one end, asshown in FIGURE 7. A cap 580 may be threadably received on the threadedopen end. By inserting additional weights, such as the Weight 59, intothe core of the counterweight 58, a moment characteristic curve will beobtained which will be shifted upwardly from that of the curve 62 inFIGURE 8say, for exampleone which approaches that of curve 66. Theadditional weights are constructed with a cylindrical shape so as toroll or rotate within the core of the counterweight 58 under the actionof gravity. As a result, the same non-sinusoidal moment characteristicis obtained as shown for the counterweight 58 alone in the curve 62.

Additionally, it may be observed that as long as the additionalcylindrical weights, such as that represented by the weight 59, are freeto roll or rotate with the hollow core, it is not essential that thecounterweight 58 be maintained in its above described pendulouslysupported, free-swinging relation to the lever members 54, but,alternatively, may be rigidly attached thereto if so desired. Such anembodiment is shown in FIGURE 10. In its preferred form, thecounterweight 58 is rigidly secured to the lever members 54, as bywelding the support tabs 58a thereto, in a manner to hold thecounterweight in a selected position or angle to the members 54. Thecounterweight 58 is thus nonrotatable as contrasted to being permittedto rotate or pivot about the mounting bolt 58b, as described inconnection with FIGURES 4 and S. In the embodiment of FIGURE 10, it willbe seen that the same relative position is maintained at all verticallyset positions for the lift mechanism 50. If desired, a handle 68, shownin phantom line, may be secured to the end of one of the lever members54 to facilitate positioning of the lift mechanism 50.

With the construction as shown in FIGURE 10, the added weight 59inserted in the core of the counterweight 58 shifts within the coreunder the influence of gravity so as to produce a similar nonsinusoidalmoment characteristic at one end of the respective lever members 54 asthat represented by the moment curve 62.

While only certain specific embodiments of the invention are shown anddescribed herein, it will, of course, be understood that many variationsand modifications may be effected without departing from the true spiritand scope of the invention. The appended claims are intended to coverall such modifications and alternative constructions that fall withintheir true scope and spirit.

What is claimed is:

1. In a portable exhaust cart, a tube lift mechanism for locating acathode ray tube having a weight within a predetermined range in aselected vertical position within predetermined limits, said lif-tmechanism including in combination:

a frame;

a pair of vertical sleeve guides mounted on said frame;

a pair of vertical support columns, each of said columns beingtelescopically received within an associated sleeve guide, said sleeveguides and said vertical support columns having a close-toleranceinterfit therebetween;

yoke means affixed to said columns at one end thereof in tube-receivingrelation to support the cathode ray tube therebetween;

lever means pivotably suspended from said frame intermediate its ends,said lever means including camming means at one end and a referencepoint at the opposite end, said camming means engaging said supportcolumns at an end opposite the end at which said yoke means is afiixedso as to support said vertical columns and cathode ray tube and toimpart vertical movement thereto when said lever means is pivoted; and

counterweighting means, said counterweighting means being positioned atsaid opposite end of said lever means adjacent said reference point,said counterweighting means exerting a balancing force acting directlyon said reference point at all set positions of the lift mechanism,

said close-tolerance interfit between said sleeve guides and verticalsupport columns providing a frictional force effective to resistmovement of the lift mechanism when at rest and maintain the same at anyset position notwithstanding a difference between the force exerted bysaid counterweighting means and that by the vertical support columns andcathode ray tube Within said predetermined weight range.

2. A mechanism to locate an object having a weight within apredetermined range in a selected vertical position within predeterminedlimits, comprising in combination:

a frame;

vertical support means on said frame to support said object, said meansincluding columnar elements movable between said predetermined limits;

lever means pivotably supported on said frame intermediate its ends,said lever means having a substantially horizontal axis and an endportion engaging a portion of said columnar support elements to impartvertical movement thereto for positioning said object;

a counterweight mounted at a reference point on the side of said levermeans opposite said one end portion, said counterweight being carried bysaid lever means in a manner whereby the center of gravity thereof ismaintained in substantial vertical alignment with said reference pointat all set positions of the mechanism;

and frictional guide means, said guide means receiving said columnarsupport elements and having an interfit therewith effective to resistmovement of said lever means when at rest and hold the same at any setposition within said predetermined limits.

3. A tube lift mechanism for vertically locating a cathode ray tubehaving a bell portion, a neck portion and a weight in a predeterminedweight range, with smoothness and accuracy, comprising in combination:

a frame;

vertical support means for supporting said cathode ray tube andincluding a yoke portion to engage the bell portion of the tube andsupport the same and vertically extending column elements;

guide means on said frame to orient the column elements of the supportmeans in tube-receiving position while permitting vertical movementthereof, said guide means and said column elements having a frictionalinterfit therebetween;

lever means rockable about a substantially common,

substantially horizontal axis, said lever means including an end portionengaging column elements to impart vertical movement thereto forpositioning said cathode ray tube;

a counterweight;

means pendulously supporting said counterweight from said lever means onthe side opposite said one end portion;

said frictional interfit between said guide means and said columnelements being such as to overcome any imbalance in the lift mechanismsystem between the counterweight and any tube weight within saidpredetermined range.

4. A tube lift mechanism for vertically locating a cathode ray tubehaving a bell portion, a neck portion and a Weight in a predeterminedrange, with smoothness and accuracy, comprising in combination:

a frame; support means adapted to seat on the bell portion of the tubeand support the same vertically, said support means having verticallyextending column elements;

guide means on said frame to orient the column elements of the supportmeans in tube-receiving position while permitting vertical movementthereof, said guide means and said column elements having a frictionalinterfit therebetween;

lever means rockable about a substantially common,

substantially horizontal axis, said lever means including an end portionengaging said column elements to impart vertical movement thereto forpositioning said cathode ray tube;

an elongated and substantially cylindrically shaped counterweight; and

means supporting said counterweight from said lever means on the sideopposite said one end portion, with its longitudinal axis substantiallyparallel to but trans verse said horizontal axis of said lever means,

said frictional interfit between said guide means and said columnelements being such as to overcome any imbalance in the lift mechanismbetween the counterweight and any tube weight within said predeterminedrange,

said counterweight having a hollow core wherein additional weights areinsertable to permit the accommodation of tubes having weights within arange higher than the aforesaid predetermined weight range.

5. A tube lift mechanism for vertically locating a cathode ray tubehaving a bell portion, a neck portion and a weight in a predeterminedrange, with smoothness and accuracy, comprising in combination:

a frame;

support means including a yoke portion adapted to seat on the bellportion of the tube to support the same vertically, said support meansfurther having vertically extending column elements;

guide means on said frame to orient the column elements of the supportmeans in tube-receiving position while permitting vertical movementthereof, said guide means and said column elements having a frictionalinterfit therebetween;

lever means rockable about a substantially common,

substantially horizontal axis, said lever means including an end portionengaging said column elements to impart vertical movement thereto forpositioning said cathode ray tube;

an elongated counterweight; and

means supporting said counterweight from said lever means on the sideopposite said one end portion with its longitudinal axis substantiallyparallel to but transverse said horizontal axis of said lever means,

said counterweight having a hollow cylindrically shaped core whereinadditional cylindrically-shaped weights are insertable so as to rotatewithin the core under the influence of gravity,

said frictional interfit between said guide means and said columnelements being such so as to maintain the lift mechanism in any setposition despite a difference in weight between said counterweight andthe cathode ray tube within said predetermined weight range.

References Cited UNITED STATES PATENTS 969,324 9/1910 Bachman 248292 X1,942,925 1/1934 Jenkins 248292 X 2,273,439 2/ 1942 Freeman 65155 X2,886,336 5/1959 Reynard 65-155 X ROY D. FRAZIER, Primary Examiner. J.F. FOSS, Assistant Examiner.

1. IN A PORTABLE EXHAUST CART, A TUBE LIFT MECHANISM FOR LOCATING ACATHODE RAY TUBE HAVING A WEIGHT WITHIN A PREDETERMINED RANGE IN ASELECTED VERTICAL POSITION WITHIN PREDETERMINED LIMITS, SAID LIFTMECHANISM INCLUDING IN COMBINATION; A FRAME; A PAIR OF VERTICAL SLEEVEGUIDES MOUNTED ON SAID FRAME; A PAIR OF VERTICAL SUPPORT COLUMNS, EACHOF SAID COLUMNS BEING TELESCOPICALLY RECEIVED WITHIN AN ASSOCIATEDSLEEVE GUIDE, SAID SLEEVE GUIDES AND SAID VERTICAL SUPPORT COLUMNSHAVING A CLOSE-TOLERANCE INTERFIT THEREBETWEEN; YOKE MEANS AFFIXED TOSAID COLUMNS AT ONE END THEREOF IN TUBE-RECEIVING RELATION TO SUPPORTTHE CATHODE RAY TUBE THEREBETWEEN; LEVER MEANS PIVOTABLY SUSPENDED FROMSAID FRAME INTERMEDIATE ITS ENDS, SAID LEVER MEANS INCLUDING CAMMINGMEANS AT ONE END AND A REFERENCE POINT AT THE OPPOSITE END, SAID CAMMINGMEANS ENGAGING SAID SUPPORT COLUMNS AT AN END OPPOSITE THE END AT WHICHSAID YOKE MEANS IS AFFIXED SO AS TO SUPPORT SAID VERTICAL COLUMNS ANDCATHODE RAY TUBE AND TO IMPART VERTICAL MOVEMENT THERETO WHEN SAID LEVERMEANS IS PIVOTED; AND COUNTERWEIGHTING MEANS, SAID COUNTERWEIGHTINGMEANS BEING POSITIONED AT SAID OPPOSITE END OF SAID LEVER MEANS ADJACENTSAID REFERENCE POINT, SAID COUNTERWEIGHTING MEANS EXERTING A BALANCINGFORCE ACTING DIRECTLY ON SAID REFERENCE POINT AT ALL SET POSITIONS OFTHE LIFT MECHANISM, SAID CLOSE-TOLERANCE INTERFIT BETWEEN SAID SLEEVEGUIDES AND VERTICAL SUPPORT COLUMNS PROVIDING A FRICTIONAL FORCEEFFECTIVE TO RESIST MOVEMENT OF THE LIFT MECHANISM WHEN AT REST ANDMAINTAIN THE SAME AT ANY SET POSITION NOTWITHSTANDING A DIFFERENCEBETWEEN THE FORCE EXERTED BY SAID COUNTERWEIGHTING MEANS AND THAT BY THEVERTICAL SUPPORT COLUMNS AND CATHODE RAY TUBE WITHIN SAID PREDETERMINEDWEIGHT RANGE.